1. Field of the Invention
This invention relates to a method for controlling the disconnection of a wireline. More particularly it concerns a method for initiating the disconnection of a wireline from a wireline tool after the wireline tool has become stuck and the wireline has possibly been damaged. The invention also includes a device for practicing the method.
2. Discussion of the Prior Art
In wireline operations in a wellbore it may happen that the wireline tool becomes stuck. Then, when the wireline tool is to be freed, or otherwise in unfavourable conditions and in incorrect manoeuvring, it may happen that one or more of the conductors of the wireline are damaged and that the unit in the wellbore will thereby be without contact with an operator on the surface.
In order to access the tool assembly with a so-called fishing tool, the wireline portion present in the wellbore must first be removed.
According to the prior art, a wireline, which is to be used in wireline operations, is provided with a weakened portion near its point of attachment in the wireline tool. The weakening is normally provided by removal of a portion of the strands of the wireline. The purpose of the weakening is that a possible wireline rupture is to be directed to this weakened portion, so that after rupturing, essentially the entire wireline can be pulled up to the surface. The wireline tool may then be retrieved by means of a so-called fishing tool.
It is evident that the method mentioned reduces the carrying capacity of the wireline to a substantial degree, and may therefore cause unnecessary rupturing of the wireline and a considerable reduction in the permitted total weight of the tool that may be used.
The invention has as its object to remedy the drawbacks of the prior art.
The object is realized according to the invention through the features specified in the description below and in the following Claims.
Prior art wireline tools are often provided with electric equipment, which is arranged to communicate with instruments on the surface during the wireline operations. Thus, it is common for the wireline to be provided with a bundle of electrical conductors, referred to below as a conductor, arranged to transfer electrical signals and possibly also electrical power for the operation of equipment in the wireline tool.